Protein Supplementation and Neuromuscular Electrical Stimulation in Persons With SCI

A spinal cord injury (SCI) is a debilitating condition, with paralysis below the lesion level as one of the main hallmarks. As a result of paralysis, together with decreased levels of physical activity and impairment-specific co-morbidities such as autonomic dysfunction, persons with SCI have a markedly reduced muscle mass. Being the major site for glucose disposal, skeletal muscle is key for the maintenance of metabolic health, while it also helps with weight management by contributing to energy expenditure at rest. As such, effective strategies to restore muscle mass in persons with SCI are warranted and can have a significant impact on metabolic health and chronic disease risk in this population.

While resistance training is widely recognised as an effective intervention to increase muscle mass in able-bodied individuals, paralysis in the lower limbs of persons with SCI precludes the use of traditional resistance training in this population. NMES has been developed to overcome this barrier and allows persons with SCI to engage in resistance exercise. Notwithstanding the evidence supporting the use of NMES on its own, combined interventions may further enhance its potential to improve health and physical function. Indeed, in the more widely studied population of older adults, that is also at risk for sarcopenia (loss of skeletal muscle mass and strength), increasing daily protein intake enhances the efficacy of resistance training to increase muscle mass.

The primary objective of this study is to determine the impact of a 12-week intervention of NMES in combination with protein supplementation when compared with NMES alone on fat free mass in the legs. Secondary objectives are to investigate the impact of the intervention on 1) markers of cardiometabolic health, namely glucose tolerance and fasting plasma lipid concentrations, 2) resting metabolic rate, and 3) skin blood flow at the level of the sacrum in response to experimental pressure. Outcomes related to tertiary objectives include perceived quality of life, neuropathic pain, body image, sleep quality and spasms; as well as free-living energy balance, physical activity and feasibility outcomes related to recruitment, adherence and participant' experiences with the intervention. It is hypothesised that NMES in combination with protein results in larger improvements in the aforementioned outcomes compared with NMES alone.

Inclusion criteria

• Motor complete spinal cord injury
• Time since injury injury >1 year

Exclusion criteria

• Spinal cord injury below T10 vertebrae
• Habitual protein intake exceeding 2g / kg body mass / day
• Having used NMES resistance training once or more per week in the last six months
• Lactose intolerant
• Any disease or medication that means the participant should not exercise
• Participation in a study involving ionising radiation in the previous 12 months